1. Field of the Invention
The present invention relates to a method for storing and transmitting moving picture data, sound data and the multiplexed data of the moving picture data and sound data and a device using the method.
2. Description of the Related Art
In recent years, according to high transmitting speed of transmission devices and high performance of reception terminals, multimedia services, such as on-demand system have been demanded, which store moving picture data, sound data and the multiplexed data of the moving picture data and sound data (hereinafter, it is referred as multimedia data) in storage devices and transmit to the multimedia data to reception terminals via a transmitter upon requests from the reception terminals.
To perform such a service flexibly and smoothly, it is required to consider contents and characteristics of the transmitter, when storing multimedia data in a storage device. It is also required to read out and transmit the multimedia data from the storage device according to various kinds of requirements sent from the reception terminals as preventing errors or minimizing the errors.
When generating multimedia data, a method for converting the multimedia data into packets for a predetermined unit and for storing the packets in the multimedia data storage device has been used.
When multimedia data is converted into packets, a packet is formed with a header, in which multimedia data information (specific information as to data length and compressing method) is described, and the multimedia data provided after the header.
Therefore, when transmitting multimedia data, which is read out from the multimedia data storage device, via a transmitter, the header information and the multimedia data coexist in one packet, and are sent out as they are.
Additionally, it is assumed to insert commercial data and the like in a multimedia data stream. For this case, it is necessary to switch the multimedia data to the commercial data while the multimedia data is transmitted. In this case, it is also required to dynamically transmit a packet information indicating the insertion point of the commercial data from a storage and transmission device to a reception terminal.
After the reception terminal obtains the information of the insertion point, and the reception terminal is initialized, it is necessary to retransmit the multimedia data from the storage and transmission device, or to compulsorily switch the multimedia data during transmitting.
On the other hand, where the transmission of the multimedia data is broken off, the end of transmitting the multimedia data has been confirmed by the use of a timer and the like.
As described above, when the multimedia data is switched, it is difficult to know a switching point on a reception terminal. It then causes that the replay of the multimedia data would be stopped with errors, or would be fallen into disorder on the reception terminal.
Further, there is a possibility that a timer for recognizing data transmission being broken off malfunctions because of temporary transmission delay, and so on, at the reception terminal.
Furthermore, there have been problems such that the time information as to the multimedia data described in a data stream may differ and that the length of the entire data stream is changed when a header packet is inserted in the data stream on transmission of the multimedia data, which has been generated and stored in a data storage.